Diptera: Tephritidae) on Ambrosia Spp

ARTHROPOD BIOLOGY Life History and Description of Immature Stages of Euaresta stigmatica (Diptera: Tephritidae) on Ambrosia spp. (Asteraceae) in Southern California

DAVID H. HEADRICK, RICHARD D. GOEDEN, AND JEFFREY A. TEERINK Department of Entomology, University of California, Riverside, CA 92521

Ann. Entomol. Soc. Am. 88(1): 58-71 (1995) ABSTRACT Euaresta stigmatica Coquillett is bivoltine and nearly monophagous on four native ragweeds, Ambrosia spp. (Asteraceae), in the southwestern United States. In southern California, larvae of the spring (F)) generation develop singly in and feed on one or both ovules of young fruiting involucres of Ambrosia ilicifolia (Gray) Payne, with a small proportion infesting the staminate involucres. Adults emerge after «*1 mo, with their reproductive organs immature. The F2 generation develops in the involucres of fall-blooming Ambrosia acanthicarpa Hooker. The egg is described and illustrated for the first time for any species of Eu- aresta. First, second, and third instars and the puparium are described and illustrated for the first time for E. stigmatica. The posterior spiracular plates of all three instars bear only three interspiracular processes, whereas the larvae and puparia of all other nonfrugivorous tephritids described to date bear four such processes. Adult behaviors described from field and laboratory studies include courtship, copulation, and territoriality. Male courtship displays include three behaviors previously undescribed for Tephritidae: a side-to-side dance, rapid side stepping, and a middle leg abduction. Hymenopterous parasitoids of E. stigmatica include two solitary, primary larval-pupal, endoparasitoids, Eurytoma sp. (Eurytomidae) and Pteromalus sp. (Ptero- malidae). Potential use of E. stigmatica as a biological control agent for ragweeds in Eurasia is discussed.

KEY WORDS Euaresta, biology, behavior

THE CURRENT STUDY OF Euaresta stigmatica Co- new knowledge of the biology, immature stages, quillett was an outgrowth of faunistic studies of the and reproductive behavior of E. stigmatica derived insect associates of ragweeds (Ambrosia spp.) and from field and laboratory studies on fall- and other Ambrosiinae (Asteraceae) in southern Cali- spring-blooming, native ragweeds in southern Cal- fornia conducted by Goeden & Ricker (1974a, b; ifornia. 1975; 1976a-c; 1986), Hilgendorf & Goeden (1983), and Goeden & Teerink (1993). The genus Materials and Methods Euaresta is native and widespread in North and Preliminary field studies and collections of E. South America (Norrbom 1993). Six of the eight stigmatica were made in 1969-1973 on Ambrosia Nearctic species occur in California (Foote et al. ilicifolia (Gray) Payne and Ambrosia acanthicarpa 1993), where E. stigmatica is common and wide- Hooker at many locations throughout southern spread. California (Goeden & Ricker 1974a, 1976b). More Little is known of the biologies of most Euaresta intensive field studies were conducted in 1991 and spp. Marlatt (1891) briefly described the biology of 1992 at the Edmund C. Jaeger Nature Preserve, Euaresta aequalis (Loew) and Phillips (1946) de- Desert Center, Riverside County, on A. ilicifolia, scribed its larvae and their feeding behavior. Both its spring-blooming host, and on or near the cam- E. aequalis and Euaresta bullans (Wiedemann) pus of the University of California, Riverside, on have been introduced into Australia for biological A. acanthicarpa, its fall-blooming host. Bulk sam- control of Xanthium spp. (Julien 1992). Foote ples of infested ragweed inflorescences were col- (1984) summarized the host-plant associations for lected at these sites and brought to the laboratory North American species of Euaresta that specialize in ice chests in an air-conditioned van and stored on Ambrosia and Xanthium spp. Batra (1979) stud- under refrigeration for subsequent dissection, ied the biology and behavior of E. bella (Loew) and measurement, photography, and description of all Euaresta festiva (Loew) in assessing them as po- life stages. tential agents for the biological control of ragweeds Immature stages were described using scanning accidentally introduced to Eurasia from North electron microscopy of two ova dissected from America (Goeden & Teerink 1993). We provide gravid, field-collected females, as well as four, sev-

adults" (Goeden & Ricker 1976a; R.D.G., unpublished data). Euaresta names used in this article follow Foote et al. (1993) and Norrbom (1993); nomenclature on larval taxonomy follows Headrick & Goeden (1991); nomenclature for wing displays by adults follows Headrick & Goeden (1991), Green et al. (1993), and Goeden et al. (1994b); ragweed inflo- rescence morphology follows Payne (1963); and plant names follow Munz (1968, 1974). Voucher specimens of reared adults of E. stigmatica and its parasitoids reside in the research collections of R.D.G.; preserved specimens of E. stigmatica larvae and puparia are stored in separate collections maintained by J.A.T. and D.H.H. Means ± SEM Fig. 1. A. ilicifolia study plant at the E. Jaeger Pre- are provided throughout diis article. serve.

Results and Discussion en, and nine each first, second, and third instars Taxonomy. Euaresta has 14 recognized species and four puparia dissected from fruiting involu- (Norrbom 1993), 6 of which occur in California cres. All specimens for microscopy were fixed in (Foote et al. 1993). The species occurring in Amer- 70% EtOH, dehydrated to absolute EtOH, soni- ica north of Mexico have recently been treated by cated for =1 min in Hexanes (Fisher, Fair Lawn, Foote et al. (1993), and those occurring in Central NJ) to remove accumulated debris, rehydrated to and South America by Norrbom (1993); both treat- distilled water, post fixed in 2% aqueous osmium ments included keys to adult stages. Descriptions tetroxide for 24 h, then dehydrated to absolute of the immature stages of E. stigmatica are provid- EtOH, critical-point dried, mounted on stubs, ed below for the first time. sputter coated with a gold-palladium alloy and ex- Egg. Twenty-five ova, dissected from field-col- amined on a JEOL JSM C35 scanning electron mi- lected females, were white, superficially smooth, croscope in the Department of Nematology, Uni- elongate-ellipsoidal, 0.17 ± 0.004 mm wide versity of California, Riverside. Micrographs were (range, 0.14-0.20) and 0.67 ± 0.01 long (range, prepared on Polaroid P/N 55 film at 15 kV accel- 0.54—0.76), with a rounded, anterior pedicel 0.02 erating voltage. mm long (Fig. 2 A and B), and a sharply tapered Adults were reared from puparia dissected from posterior end measuring 0.09 ± 0.003 mm long fruiting involucres held in individual, glass-shell vi- (range, 0.06-0.12). Examination with light micros- als in humidity chambers at 22-24°C and 76% RH. copy showed the posterior end to be free of em- Newly emerged adults were isolated in clear plastic bryonic tissues. Sixteen eggs dissected from plant cages (850 ml) fitted with screened lids for venti- tissue averaged 0.17 ± 0.007 mm in width (range, lation, basal water reservoirs, and provisioned with 0.14-0.30) and 0.64 ± 0.008 mm in length (range, honey and protein hydrolyzate (Headrick & Goe- 0.58-0.71). den 1993). Five mating trials lasting 2 wk each This is the first description of the egg of any were conducted with virgin adults held in dispos- species of Euaresta. The general size and shape of able, plastic petri dish arenas (10-cm diameter) E. stigmatica eggs are similar to those of Paroxyna (Headrick & Goeden 1993). Mating trials were genalis (Thomson) (Goeden et al. 1994b). How- conducted in the laboratory under artificial lighting ever, the eggs of E. stigmatica are more parallel between 0900 and 1800 hours PST. sided than described for other nonfrugivorous Field observations of reproductive behaviors tephritid species (cf. Goeden & Headrick 1991a, were made for at least 4 h each day on 25 February b; Headrick & Goeden 1993; Goeden et al. 1994b). and 4, 11, 18, and 24 March 1992, at the Jaeger The elongate posterior end of E. stigmatica. eggs Reserve, where A. ilicifolia plants were located in also differs from other nonfrugivorous tephritid a deep, N/S-oriented, dry, sandy wash at an ele- eggs described thus far, and its function remains vation of 850 m. A single plant (^l by 2 m wide unknown. and 1 m tall) located between large granite boul- Third Instar. Third instar superficially smooth, ders was the primary study location (Fig. 1). This barrel-shaped, slightly tapered anteriorly, rounded plant's stems (0.3-0.6 m long) had shorter branch- posteriorly (Fig. 3A); integument white with the es, spiny holly-like leaves, and apical spikes of sta- caudal segment black; thoracic segments with mi- m in ate involucres above the separate, pistillate, nute acanthae dorsally, abdominal intersegmental fruiting involucres. This study area and this same area circumscribed by minute acanthae; gnatho- plant had been noted by R.D.G. 20 yr earlier dur- cephalon conical, laterally flattened, smooth with ing a study of the insect fauna of this native rag- few rugose pads dorsally, broad serrated rugose weed to host "an abundance of E. stigmatica pads laterally along mouth lumen (Fig. 3B, 1 and 60 ANNALS OF THE ENTOMOLOGICAL SOCIETY OF AMERICA Vol. 88, no. 1

=0.025 mm long (Fig. 3H, 1), and three interspiracular processes with two to four branches each, the longest measuring 0.015 mm (Fig. 3H, 2); stelex sensilla (Fig. 3G, 2) surrounding margin of caudal segment in four-dorsal, six-ventral arrange- ment; caudal segment additionally bearing a pair of verruciform sensilla ventrad of the spiracular plates (Fig. 3G, 3). Euaresta stigmatica belongs to the tribe Tephri- tini, which also includes Dioxyna, Neotephritis, Paroxyna, Tephritis, Trupanea, and many other genera (Foote et al. 1993). The general larval body shape is closer to that of Trupanea and Paroxyna than to Dioxyna, Neotephritis, and Tephritis species previously examined (Novak & Foote 1968; Goeden & Headrick 1991b; Headrick & Goeden 1991; Goeden et al. 1993, 1994b; unpublished data). Trupanea species can be distinguished from E. stigmatica by the rows of rugose pads circum- scribing the prothorax (Headrick & Goeden 1991; unpublished data). In E. stigmatica, the mouth- hooks of the larvae appear to have been worn down considerably, perhaps caused by the tough- ness of the seed tissues. The number of sensilla in the lateral spiracular complex differ between the metathoracic and abdominal segments in E. stigmatica. One other species, Acuirina thoracica Cur- ran has shown similar differences; however, the number of sensilla differed between the mesotho- racic and the metathoracic and abdominal segments (Headrick & Goeden 1993). Phillips (1946) described the mature larva of E. Fig. 2. Egg of E. stigmatica: (A) habitus, anterior end aequalis. According to her description, E. aequalis at left; (B) detail of pedicel, showing aeropyles. is very similar morphologically to E. stigmatica with a few minor differences: the anterior thoracic spiracles in E. aequalis bear 9-10 papillae (versus D, 1); paired dorsal sensory organs lie mediad of 5 in stigmatica), and the caudal segment of E. ae- anterior sensory lobes, each consisting of single qualis has four interspiracular processes with two dome-shaped papilla (Fig. 3B, 2 and C, 1); anterior to three branches each, whereas, as noted above, sensory lobes bearing terminal sensory organ (Fig. E. stigmatica has only three processes each with 3C, 2), pit sensory organ (Fig. 3C, 3), lateral sen- two to four branches, the only tephritid species sory organ (Fig. 3C, 4) supralateral sensory organ known to have only three interspiracular processes. (Fig. 3C, 5); stomal sense organs lie ventrad of an- In E. stigmatica and E. aequalis, the sensilla ven- terior sensory lobes, near mouth lumen (Fig. 3B, trad of the posterior spiracular plates are com- 3 and C, 6); mouth hooks bidentate, teeth stout, posed of a single verruciform papilla with a central bluntly conical (Fig. 3B, 4 and D, 2); median oral pore. Other tephritid species have paired com- lobe laterally compressed, tapers apically to a fine pound sensory organs composed of a stelex and point; attached ventrally to labial lobe (Fig. 3D, 3); medusoid sensillum (cf. Goeden & Headrick labial lobe with paired sensilla (Fig. 3B, 5); lateral 1991b; Goeden et al. 1993; 1994a, b; unpublished and ventrolateral lobes each bearing a verrucate data). sensillum with a central pore (Fig. 3B, 6 and 7); Second Instar. Second instar elongate, cylindri- anterior thoracic spiracles located dorsolaterally on cal, tapered anteriorly, rounded posteriorly (Fig. posterior margin of prothorax, each bearing five, 4A); integument creamy white; gnathocephalon rounded papillae (Fig. 3E); lateral spiracular com- conical, smooth with few rugose pads (Fig. 4B), plex on meso- and metathorax composed of small two small, serrated pads laterad of stomal sense open spiracle (Fig. 3F, 1) and two, verruciform organs (Fig. 4B, 1); dorsal sensory organs lie dor- sensilla (Fig. 3F, 2); lateral spiracular complex on somedially of anterior sensory lobes, each consist- abdominal segments composed of an open spiracle ing of a single, dome-shaped papilla (Fig. 4C, 1); and single verruciform sensillum; caudal segment anterior sensory lobes flattened, bearing terminal smooth with no acanthae, bearing nonprominent, sensory organ (Fig. 4C, 2), pit sensory organ (Fig. noncontiguous posterior spiracular plates (Fig. 3G, 4C, 3), lateral sensory organ (Fig. 4C, 4), supralat- 1); each plate with three elongate-oval rimae eral sensory organ (Fig. 4C, 5); stomal sense organs January 1995 HEADRICK ET AL.: LIFE HISTORY OF E. stigmatica 61

Fig. 3. Third instar of E. stigmatica: (A) habitus, anterior to left; (B) gnathocephalon, left ventrolateral view, (1) serrated rugose pads, (2) dorsal sensory organ, (3) stomal sense organ, (4) mouth hooks, (5) labial lobe sensilla, (6) lateral sensillum, (7) ventrolateral sensillum; (C) gnathocephalon, left lateral view, (1) dorsal sensory organ, (2) terminal sensory organ, (3) pit sensory organ, (4) lateral sensory organ, (5) supralateral sensory organ, (6) stomal sense organ; (D) gnathocephalon, anterior view, (1) serrated rugose pads, (2) mouth hooks, (3) median oral lobe; (E) anterior thoracic spiracles; (F) lateral spiracular complex, metathorax, (1) spiracle, (2) verruciform sensillum; (G) caudal segment, (1) posterior spiracular plate, (2) stelex sensillum, (3) verruciform sensillum; (H) caudal segment, posterior spiracular plate, (1) rimae, (2) interspiracular process. 62 ANNALS OF THE ENTOMOLOGICAL SOCIETY OF AMERICA Vol. 88, no. 1

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Fig. 4. Second instar of E. stigmatica: (A) habitus, anterior to left; (B) gnathocephalon, left ventrolateral view, (1) serrated rugose pads, (2) mouth hooks, (3) median oral lobe, (4) lateral sensillum, (5) ventrolateral sensillum; (C) gnathocephalon, left lateral view, (1) dorsal sensory organ, (2) terminal sensory organ, (3) pit sensory organ, (4) lateral sensory organ, (5) supralateral sensory organ, (6) stomal sense organ; (D) gnathocephalon, ventral view, (1) mouth hooks, (2) median oral lobe, (3) labial lobe sensilla; (E) anterior thoracic spiracle; (F) caudal segment, posterior spiracular plate, (1) rimae, (2) interspiracular process. lie ventrolaterad of anterior sensory lobes (Fig. 4C, lobe bearing paired sensilla (Fig. 4D, 3); lateral 6); mouth hooks bidentate, teeth conical, sharply and ventrolateral sensilla present, each bearing pointed (Fig. 4B, 2 and D, 1); median oral lobe verruciform sensillum (Fig. 4B, 4 and 5); anterior laterally compressed, smooth, rounded anteriorly, thoracic spiracles dorsolaterad on posterior margin attached to labial lobe (Fig. 4B, 3 and D, 2); labial of prothorax, each bearing five oval papillae (Fig. January .1995 HEADRICK ET AL.: LIFE HISTORY OF E. stigmatica 63

Fig. 5. First instar of E. stigmatica: (A) habitus, ventral view, anterior to left; (B) gnathocephalon, left lateral view, (1) dorsal sensory organ, (2) terminal sensory organ, (3) pit sensory organ, (4) lateral sensory organ, (5) supralateral sensory organ, (6) stomal sense organ; (C) gnathocephalon, ventrolateral view, (1) mouth hooks, (2) median oral lobe, (3) labial lobe sensilla, (4) lateral sensillum, (5) ventrolateral sensillum; (D) caudal segment, posterior spiracular plates, (1) rimae, (2) interspiracular process.

4E); caudal segment bearing posterior spiracular lobes (Fig. 5B, 1); anterior sensory lobes flattened, plates (Fig. 4F); each plate with three oval rimae not well defined, bearing the terminal sensory or- =0.015 mm long (Fig. 4F, 1), and three, interspi- gan (Fig. 5B, 2); pit sensory organ (Fig. 5B, 3); racular processes each with one to three branches, lateral sensory organ (Fig. 5B, 4), supralateral sen- longest measuring 0.01 mm (Fig. 4F, 2). sory organ (Fig. 5B, 5); stomal sense organs small, The second instar differs from the third instar not well defined, lie ventrad of anterior sensory in its general body shape, being more cylindrical lobes (Fig. 5B, 6); mouth hooks bidentate, conical, than barrel shaped. The gnathocephalon of the sharply pointed (Fig. 5C, 1); median oral lobe lat- second instar has only two serrated rugose pads erally compressed, tapered anteriorly, attached to laterad of the stomal sense organ. The median oral labial lobe (Fig. 5C, 2); labial lobe bears two sen- lobe is not as distinctly tapered as in the third in- silla (Fig. 5C, 3); lateral and ventrolateral sensilla star. Because of the wrinkled nature of the second present (Fig. 5C, 4 and 5); anterior thoracic spira- instar prepared for scanning electron microscopy, cles absent; caudal segment bears the posterior spi- the lateral spiracular complex was not observed, racular plates (Fig. 5D); each plate bears two oval nor were the caudal sensilla. rimae, =0.004 mm in length (Fig. 5D, 1), and First Instar. First instar cylindrical, rounded an- three, stout, spine-like interspiracular processes, teriorly and posteriorly, thoracic segments smooth, the longest measuring 0.003 mm (Fig. 5D, 2); ste- lacking the minute acanthae which circumscribe lex sensilla located around margin of caudal seg- the abdominal segments (Fig. 5A); gnathocephalon ment. conical, smooth with no rugose pads (Fig. 5C); First instars are more cylindrical than second in- dorsal sensory organs flattened, indistinct round stars. There are no rugose pads on the gnathoceph- papillae located dorsomediad of anterior sensory alon of first instars, the anterior sensory lobes are 64 ANNALS OF THE ENTOMOLOGICAL SOCIETY OF AMERICA Vol. 88, no. 1 not well defined, and the sensory organs are indistinct. The stomal sense organ is poorly defined compared with second instars. The respiratory system undergoes substantial morphogenesis between the first and second instars. First-instar E. stigmatica lack anterior thoracic spiracles; the lateral spiracles were not observed and the posterior spiracular plates bear two, small rimae. Puparium. Puparia were either entirely dark or darkened only on both ends, elongate-ellipsoidal, truncated anteriorly, rounded posteriorly, superficially smooth, thoracic segments with minute acanthae dorsally, abdominal intersegmental areas circumscribed by minute acanthae (Fig. 6A); 16 intact puparia measured 2.84 ± 0.07 mm long (range, 2.03-3.12) and 1.39 ± 0.035 mm wide (range, 1.07-1.58); anterior end bearing invagination scar (Fig. 6B, 1) and raised anterior thoracic spiracles dorsolaterad of invagination scar (Fig. 6B, 2); caudal segment bears the posterior spiracular plates (Fig. 6C); each plate bears three oval rimae, =0.02 mm long (Fig. 6C, 1), and three interspiracular processes, two to five branches each, longest measuring 0.015 mm (Fig. 6C, 2); verruciform sensilla ventrad of spiracular plates are distinct (Fig. 6C, 3). Distribution and Host Range. E. stignvztica is strictly Nearctic (Norrbom 1993). Its distribution north of Mexico was mapped by Foote et al. (1993). It appears to be common in the Southwest, but there are also records from Kansas and Mon- tana. This tephritid is nearly monophagous, as known to date, reproducing solely in the involucres of four native ragweeds: A. acanthicarpa and A. ilicifolia in southern California (Goeden & Ricker 1974a, 1976b) and A. ambrosiodes (Cavanilles) Payne, A. deltoidea (Torrey) Payne, and A. ilicifolia in southwestern Arizona (Foote 1984). Biology. Egg. The female pierces the outer seed coat with her aculeus and inserts a single egg for approximately two-thirds of its length, pedicel last into an ovule within a fruiting involucre. In laboratory cages and field-collected samples, egg place- ment was either near the base or apex of a fruiting involucre (Fig. 7A). Egg pedicels typically protrud- ed from the seed coats; however, some eggs were inserted entirely beneath the seed coat and lay hid- den lengthwise, alongside an ovule. Two seeds develop within each fruiting involucre in individual Fig. 6. Puparium of E. stigmatica: (A) habitus, ante- chambers separated by a thin septum. In A. ilici- rior to left; (B) anterior end, (1) invagination scar, (2) folia, the larva attacked both seeds in 41 of 126 anterior thoracic spiracle; (C) caudal segment, posterior (33%) infested involucres. In contrast, in A. acan- spiracular plate, (1) rimae, (2) interspiracular process, (3) thicarpa the larva attacked only one seed in each verruciform sensillum. of 57 infested involucres examined. Multiple ovi- positions into individual involucres were rare; 2 larvae occurred in only 5 of 126 (4%) infested invo- and four females were reared from bulk samples lucres of A. ilicifolia and none of A. acanthicarpa. of isolated staminate involucres of A. acanthicarpa. The staminate, pollen-bearing involucres of A. Larva. First instars eclose after =3-5 d, exit acanthicarpa and A. ilicifolia also are occasionally from the posterior end of the egg after first rotat- infested by E. stigmatica. Eggs were laid singly into ing 180° while still an embryo, then tunnel into and the staminate florets of 3 of 137 (2%) staminate initially feed at the base of the ovule. Two invo- involucres of A. ilicifolia examined. Twelve males lucres were dissected in which the attacked ovules January 1995 HEADRICK ET AL.: LIFE HISTORY OF E. stigmatica 65

Fig. 7. Life stages of E. stigmatica from A. ilicifolia (A-C, E-G) and A. acanthicarpa (D): (A) Egg inserted into ovule of fruiting involucre, (B) second instar feeding in ovule, (C) third instar in feeding chamber in fruiting involucre, (D) third instar in feeding chamber, (E) view of excavated exit window from inside fruiting involucre, (F) third instar larva feeding centrally among florets of staminate involucre, (G) puparium in excavated chamber, (H) adult female, (1) pair in copula on fruiting involucre of A. ilicifolia taken in nature. 66 ANNALS OF THE ENTOMOLOGICAL SOCIETY OF AMERICA Vol. 88, no. 1

Table 1. Distribution, abundance, and sex ratios of E. stigma tic a on A. ilicifolia, Ed. Jaeger Preserve, spring 1992

No. March No. No. No. Sex No. males Mated adults Range Total rati0 airs date stems per stein males females Courting Resting P 4 40 2.1 1-4 64 29 93 2.2:1 11 14 1.9 1-4 35 12 47 2.9:1 31 18 30 1.5 1-3 63 33 96 1.9:1 58 24 30 1.5 1-4 54 29 83 1.8:1 49 had aborted and the larvae within had died. In mature, and required 4—6 wk of feeding on protein one-third of the 157 fruiting involucres of A. ili- hydrolyzate and honey to develop eggs in individ- cifolia examined in which one ovule was infested ual laboratory cagings. Females collected from by a first instar, the other ovule within the invo- rendezvous sites in early spring (see discussion be- lucre had died and shriveled and was rendered un- low) were also reproductively immature, but col- suitable for continued larval feeding and develop- lections of females from the same plant 1 wk later ment. First instars molted after =1 wk and showed them to contain full-sized ova (n = 3). continued to feed as second instars on the remain- Abundance. Field observations were made during ovule in involucres of A. ilicifolia (Fig. 7B). By ing 5 wk at the Jaeger Reserve study site beginning the second molt, after =2 wk, much of the second on 25 February 1992, when =20 adults were re- ovule also was consumed. The uninfested seeds corded on the main study plant, the "rendezvous normally are white inside, but infested seeds be- site" (Zwolfer 1974), but only 3 or fewer were come darkly stained, dried, and lined with frass found on other, nearby plants of comparable size. compacted at both ends of the open ellipsoidal Table 1 records the numbers of adults present on feeding chamber (Fig. 7C). Third instars continue this plant during the next 4 wk beginning 4 March to excavate the fruiting involucres, leaving intact 1992. Males consistently outnumbered females, only the dried, hard, and darkened fruit coats in but the total number of adults fluctuated consid- both A. ilicifolia (Fig. 7C) and A. acanthicarpa erably from week to week. The number of adults (Fig. 7D). Most growth takes place during this per stem were distributed relatively uniformally third stadium, which lasts for =1 wk. The mature over the entire rendezvous plant during the obser- third instar is approximately half the length and vation period. Generally, from one to four individ- about as wide as its feeding chamber. Before pu- uals were observed on each stem, for averages of pariation, the third instar scrapes away a small exit 1.5—2.1 adults per stem during the study period hole in the wall at the base of the involucre, leaving (Table 1). Adults of the next generation began a translucent, circular, epidermal window (Fig. emerging 2-3 wk later. The daily pattern of abun- 7E). Windows averaged 0.58 ± 0.015 mm in di- dance of F2 flies of both sexes also was monitored ameter (n = 25; range, 0.43-0.73) and were locat- for the next 4 wk. Both sexes were abundant and ed 0.86 ± 0.047 mm from the stalk of the invo- active by 0930 hours, the greatest number of mat- lucre (n = 25; range, 0.51-1.47). ed pairs was observed at —1200 hours (maximum, In staminate involucres, all larval stages feed 9) on each of the observation days, and the number within the pollen-bearing, staminate florets. No of single males declined thereafter. The number of exit window is made and third instars orient with single females ovipositing remained high until their heads directed outward in the hollowed-out =1500 hours daily, after which adults were rarely feeding cavity before pupariation (Fig. 7F). observed. Puparium. Pupariation by E. stigmatica in a Wing Displays. Under field conditions, E. stig- fruiting involucre is unusual in that the third instar matica exhibited enantion, lofting, and rarely ha- does not face outward, but remains oriented with mation and asynchronous supination as defined by its head facing the base of the involucre, allowing Headrick & Goeden (1991), Green et al. (1993), the emerging adult direct access to the exit hole and Goeden et al. (1994b). The most common dis- (Fig. 7G). In contrast, most, but not all (R.D.G. & play by both sexes in field and laboratory obser- J.A.T., unpublished data), tephritids that we have vations was a unique form of enantion in which studied position their exit windows toward the apex the wings were held flat over the dorsum and ex- of a gall, or infested branch or stem (cf. Goeden tended forward synchronously from the midline of 1988, Headrick & Goeden 1990, Goeden & Head- the body through =90° without supination. The ex- rick 1991b, Goeden et al. 1993). tensions occurred in rapid bursts lasting ^ls, with Adult. The spring, Fx generation of adults reared short pauses of 1-2 s between each episode. Males from A. ilicifolia lived an average of 76 ± 3.5 d (n exhibited this type of enantion most often and as = 145; range, 4-155) (Fig. 7H). The fall, F2 gen- a continuous part of their territorial display. Males eration of adults from A. acanthicarpa were longer also exhibited this enantion while in copula, es- lived, averaging 168 ± 17.7 d (n = 46; range, 24- pecially when the females moved or otherwise 312). Females always emerged reproductively im- were disturbed. January 1995 HEADRICK ET AL.: LIFE HISTORY OF E. stigmatica 67

In contrast, females continually moved about a plant while probing for ovipositional sites with the apices of their ovipositors in immature fruiting involucres, and much less frequently, in the staminate involucres. As they explored the plant in this manner, they encountered patrolling males perched on leaves. Males initially raised and lowered their fore legs once to any individual walking onto their leaf surface (n = 24). Other males answered in kind and combat usually ensued; however, females did not respond with any observable body movement and the males immediately initi- ated courtship (n — 14). Males faced females, extended their mouthparts fully, distended their abdominal pleura, and crouched (Fig. 8A). If the females remained, males lofted their wings fully upright and began rocking their bodies from side to side rapidly for brief episodes lasting —2-3 s (Fig. 8A). Males did not keep their mouthparts extended during their courtship displays, but while a male rocked or danced, he extended his mouthparts and tried to place them against the female's mouthparts (Fig. 8A). The female responded by extending her mouthparts toward the male and briefly touching them or by extending them and moving toward the male as he backed away. No fluids were observed to be ex- Fig. 8. (A) Male courtship display (drawn from field changed, as reported for several other species of photo), male on right, arrows denote distended abdomi- tephritids whose premating trophallaxis required nal pleura, extended mouth parts, lofted wings, double- several minutes (Stolzfus & Foote 1965, Headrick headed arrow denotes direction of lofting/dance display. & Goeden 1990, Goeden & Headrick 1992). When (B) Male positioned behind female for aculeus exsertion a male displayed wing lofting/dancing during (drawn from field photo), arrow denotes male abdomen courtship, he stilted on his legs with his abdomen curled underneath the body. held higher than the rest of his body. During this dance, the male's tarsi did not move, only his body. This side-to-side dance was repeated often, and a Males displayed an exaggerated form of lofting male generally held his wings lofted until he during courtship displays with females. The wings moved behind a female. were lofted to 90°, perpendicular to the long axis Unreceptive females never permitted males to of the body and parallel to each other (Fig. 8A). move into position behind them. The courting They were not vibrated while lofted but rather male moved sideways, side-stepping rapidly while held in this position, while the male rocked his facing the female, so as to position himself behind entire body vigorously from side to side (see her. However, the unreceptive female held her Courtship section below). Wing lofting was similar wings flat and overlapped on her dorsum and to that of Paroxyna genalis (Goeden et al. 1994b), turned in one spot, always facing the side-stepping but in E. stigmatica the wings were held lofted at male. Males often switched directions and side- 90° with respect to the substrate and parallel to stepped rapidly back and forth through =180°. If each other. Only males displayed lofting in E. stig- a female remained unreceptive, the male stopped matica. Males also displayed lofting in territorial side stepping, raised his front legs above his head, bouts with other males, in which the wings were lowered his anterior end, extended his mouthparts, extended to only 45° above the body, parallel to and either resumed side stepping in arcs around the midline of the body, with the wing blades part- the female or began a lofting/dance display. ed =45°. However, if the female was receptive, she al- Courtship. In the field, males usually were ob- lowed the male to get into position behind her. served on sunlit leaves while walking about the ad- Once positioned behind the female, the male re- axial surfaces, observing, and orienting to face turned his wings to their resting position flat on his nearby flies. Little site fidelity was shown by males, dorsum and deflated his abdominal pleura. He as they only remained on a particular leaf for up stood behind her, sometimes placed his fore tarsi to 15 min, and often vacated a leaf after combat on the tips of her wings, curled his abdomen for- with other males whether they won or lost. How- ward beneath him, placed his epandrium at the ever, all courtship and territorial displays by males apex of her ovipositor, and waited (Fig. 8B). If the took place on the adaxial surfaces of leaves. female was unreceptive at this point, she did not 68 ANNALS OF THE ENTOMOLOGICAL SOCIETY OF AMERICA Vol. 88, no. 1 exert her aculeus, and the male returned to face mated pair remained quiet, usually staying on or her again from the front. Once in front of her near the same leaf, and occasionally moved from again, he raised both of his middle legs once, syn- sunlight into shade. chronously, high above his thorax, then dropped Encounters between males and mating pairs them to the substrate. After this middle leg ab- were frequent because of the high numbers of induction, he again began his lofting/dance display. dividuals on the plant (Table 1). Single males ap- After a few more episodes of the lofting/dance dis- proached mating pairs and displayed toward the play, he again maneuvered behind the female, low- females. Some males attempted to mount mating ered his wings, deflated his pleura, and curled his pairs. These intruding males were met with ag- abdomen beneath him so his epandrium again gressive lunges by the copulating females and wing touched the apex of her oviscape. displays by the copulating males. These interac- Courtship displays with individual females con- tions always ended with the intruding males de- tinued for as long as a half hour or until an unre- parting (n = 5). ceptive female walked away. There were many dis- Timed copulations lasted an average of 1 h in tractions for courting males, such as other males the field (n = 9 observed from initiation to dis- moving in and initiating combat. Because of the engagement). Disengagement was quick. A male high densities of flies on the study plant (Table 1), turned to one side, stepped down from the fe- some males were observed to court two females male's dorsum onto the substrate, and moved away simultaneously, all the while intermittently fighting from her while pulling his aedeagus from her acu- with intruding males. The courting males were leus. Once parted, they sat still apart from each able to switch from their courtship displays to other and groomed for a short time. Then, either fighting displays (described below) and back again one, and ultimately both flies moved off the leaf without pause. and onto other parts of the branch or nearby Copulatory Induction Behavior. Males remained branches. In one instance, a female in copula passive behind females, with their epandrium walked away from the male while he remained sta- poised for the exsertion of the aculeus, while they tionary. She continued forward, pulling his abdo- sometimes touched the wing tips of the females men forward underneath him. He stepped back- with their fore tarsi. Thus, unlike other tephritid ward away from the female, and his aedeagus males studied to date, E. stigmatica males do not pulled free. This male then moved toward the fe- mount females before exsertion of the aculeus, and male and began courtship displays, but soon thus, do not rub their hind or middle legs on the stopped his displays and moved away from the fe- oviscape of the female to stimulate exsertion of the male. aculeus. Oviposition. Females did not oviposit directly af- Copulation. The male engaged the exserted acu- ter disengagement from copulation, but rather leus with his surstyli as he mounted the female and usually sat grooming. Oviposition was observed wrapped his front legs around the middle of her most commonly in the afternoon, i.e., after =1300 abdomen. As he moved forward, her ovipositor was hours. Females walked upon and examined fruiting raised slightly. In this initial position, the male was involucres of certain sizes, i.e., >7 mm in diameter, stilted on his extended legs above the female, with or those with two stigmas exposed. They probed his head over the middle of her abdomen, and his while facing away from the center of the involucre, abdomen curled downward (Fig. 71). The aculeus where the tips of their oviscapes were directed. remained exserted, and pushed the male's abdo- Oviposition followed probing and lasted ^S-S min. men backward. At this point the male began rub- Females remained on the fruit after oviposition bing the oviscape with his hind legs, and intermit- and groomed and rested. tently displayed enantion, typical of copulatory Feeding. Feeding by adults was readily observed induction behavior displays of other nonfrugivo- in laboratory arenas and in field observations. rous tephritid males such as Aciurina thoracica Adults readily fed at water and protein sources Curran (Headrick & Goeden 1993) and Trupanea provided in arenas and produced droplets as ob- californica Malloch (Headrick & Goeden 1991). served and described for other tephritid species The female sat quietly with her wings spread and (cf. Goeden & Headrick 1992; Headrick & Goe- mouthparts pumping during copulation. As inser- den 1991, 1993; Green et al. 1993). Adults in the tion of the aedeagus proceeded, the aculeus was field touched their mouthparts to leaves and slowly retracted and the male moved slightly for- branches, to fruiting and staminate involucres, and ward on the female. In his final position, the male's to the carcasses of dead arthropods. abdomen was bent downward only slightly, both his hind and middle legs were on the substrate, Territoriality. A single leaf was patrolled by a and his front legs grasped the abdomen of the female, and he displayed his front legs to any indi- male near her thorax. The final mating posture was vidual that moved onto this leaf. Intruding males achieved 2-3 min after initial exsertion of the acu- answered in kind and ritual combat began (n = leus. The female walked around while the male 10). During this combat, males faced each other continued to use his middle and hind legs to with their abdominal pleura distended, wings par- groom or drum on the female's abdomen. The tially lofted, and mouthparts extended. Battles began with the males drumming their raised front January 1995 HEADRICK ET AL.: LIFE HISTORY OF E. stigmatica 69 legs together. The males then dropped to the sub- did not court ovipositing females. Also according strate, lowered their wings, and pressed their ex- to Batra (1979), males of both E. bella and E. fes- tended mouthparts together. They began to move tiva established territories, but of differing sizes. from side to side asynchronously to each other, E. bella males had a territory of one or two leaves, rubbing their extended mouthparts together at which they occupied for a few hours; however, E. each pass. Some males moved off the leaf after this festiva males had a territory of 1 m2, which indi- initial encounter, but other battles became more vidual males occupied for more than a few hours involved. If both males remained, they continued (Batra 1979). Copulation for E. festiva occurred the battle by raising their front legs again and en- late in the afternoon, and lasted for «1 h (n = 2); gaged in mouthpart rubbing. After this behavior, copulation for E. bella occurred throughout the each male tried to turn sideways toward the other day and lasted 20-60 min (n = 15) (Batra 1979). male and bat him with an extended, supinated The behavioral similarities of both of these spe- wing. Each male also tried to grasp the others cies, and especially E. festiva, to E. stigmatica is wings with his front legs in a leg-lock, i.e., trapping an example of the many shared behavioral attri- the wing blade between the fore tibia and femur. butes of congeners and helps to substantiate the They continued to wrestle and batter each other closeness of these three species hypothesized by until one turned and moved away. The losers were Norrbom (1993). Behaviors observed in all three usually chased by the victors until the former were species include wing enantion or "rapid flicks of on another branch or out of sight. Combat sessions both wings simultaneously," asynchronous supina- lasted up to 5 min and ended with the victor re- tion or "alternate wing waving with vibration" turning or not returning to their leaf. Females (though less common in E. stigmatica), mouthpart were not attracted to males in combat. Male com- contact, and territoriality. E. stigmatica and E. fes- bat in other tephritid species has many similar tiva also share two more features: males curling components; e.g., appendage displays, mouth part their abdomens underneath them and holding extention and touching, stilting and wrestling, but their wings flat over their dosa while sitting behind these behaviors are rarely observed in natural field females. However, E. stigmatica did not court ovi- settings (Boyce 1934, Dodson 1985, Headrick & positing females as did E. festiva, and copulations Goeden 1990; unpublished data). took place only on the upper surfaces of leaves Batra (1979) described the courtship and mating patrolled or defended by males. Other behaviors behavior of E. bella and E. festiva from Ambrosia reported here for E. stigmatica and not reported artemisiifolia L. and A. trijida L., respectively. E. by Batra (1979) for E. bella and E. festiva include bella and E. festiva adults were most active in the wing lofting, abdominal pleura distension, males late afternoon and both tended to remain on or raising their front legs as an initial greeting, male near their host plants (Batra 1979). E. stigmatica lofting/dance during courtship, a courting male's adults were active from =s0900 to 1500 hours but rapid side stepping to maneuver behind a female, females were generally more abundant and active a courting male raising his middle legs after initial after =1300 hours. rejection by an unreceptive female, and male ritual Courtship behaviors for E. bella and E. festiva combat. appear similar to those of E. stigmatica, except in Seasonal History. E. bella and E. festiva are terms of interpretation. Batra (1979) listed 10 both monophagous and univoltine (Foote 1984, courtship behavior "patterns" observed for both E. Foote et al. 1993); whereas E. stigmatica is bivol- bella and E. festiva, "(1) visual orientation, (2) al- tine in southern California, producing a spring ternate wing waving with vibration, (3) both wings generation on A. ilicifolia and a fall generation on extended horizontally, (4) both wings extended A. acanthicarpa (B. A. Foote reported rearing a with proboscis extended, (5) both wings extended spring generation of E. stigmatica from A. ambro- with head butting, (6) tapping with front feet, (7) sioides in southwest Arizona and noted that anoth- rapid flicks of both wings simultaneously, (8) ter- er host-plant species must be used by these adults ritoriality (lekking), (9) male following female, ab- because A. ambrosioides was no longer producing domen curved, (10) male following female, wings involucres, personal communication). E. bella flattened against abdomen." Interpreting the adults are found from mid-June to late September courtship sequence for E. bella and E. festiva as in Ohio and Maryland, whereas E. festiva adults described by Batra (1979) is difficult because other appear in July in Maryland and reach their peak behaviors beside courtship were involved simulta- abundance in mid-September (Batra 1979, Foote neously; e.g., aggression, male-male interactions, 1984). Both E. bella and E. festiva overwinter as and female-female interactions. From the data she diapausing larvae in fruiting involucres (Foote presented, we interpret that during courtship, 1965, 1984; Batra 1979). males approached females with a wing display oth- Adults of E. bella and E. festiva females er than lofting; mouthpart contact was made; emerged reproductively immature, but after a males of E. festiva followed females for courtship month mature, then oviposit for another month with their abdomens curved, their wings flat over (Batra 1979). This compares with the similar pre- their dorsa, and male courtship took place while reproductive period of 4—6 wk observed in the cur- females were ovipositing; whereas, E. bella males rent study with caged Fj adults of E. stigmatica 70 ANNALS OF THE ENTOMOLOGICAL SOCIETY OF AMERICA Vol. 88, no. 1 reared from involucres of A. ilicifolia collected at lied taxonomically to A. artemisiifolia and A. trijida the Jaeger Reserve study site. These Fi adults in (Payne 1963), but unlike them has not been acci- nature apparently oversummer and reproduce in dentally exported from North America as an agri- the fall in southern California on the widespread, cultural weed and a growing, worrisome source of annual ragweed, A. acanthicarpa. E. stiginatica aeroallergenic pollen in Eurasia. Therefore, if it then overwinters as F2 adults that rendezvous on can be successfully induced to attack these two A. ilicifolia in the Colorado Desert in the spring to ragweeds, E. stiginatica obtained from A. acanthi- reproduce and complete the cycle. Reproduction carpa, in comparison with E. bella and E. festiva by E. bella and E. festiva was concurrent with the attacking their natural host plants, may provide a flowering of their sole hosts (Batra 1979, Foote good test of the so-called "new-host theory" of 1984), as with bivoltine E. stiginatica on its two Hokkanen & Pimentel (1984). It was in this con- hosts in southern California. text that the current study of E. stiginatica was Natural Enemies. The principal natural ene- undertaken, as our contribution to a new cooper- mies of immature E. stiginatica in fruiting and sta- ative research and natural enemy exchange pro- minate involucres of A. acanthicarpa and A. ilici- gram between Agriculture Canada and the Acad- folia were the solitary, primary, larval-pupal, emy of Agricultural Sciences of the People's endoparasitic, chalcidoid Hymenoptera, Eurytoma Republic of China involving, among other projects, sp. (Eurytomidae) and Pteromalus sp. (Pteromali- the biological control of ragweeds (Goeden & dae). Both wasp genera are commonly associated Teerink 1993; R.D.G.; unpublished data). with other nonfnigivorous, florivorous Tephritidae in southern California, but additional taxonomic Acknowledgments study is needed to determine how many and what species of these parasitoids are involved, for which We thank A. C. Sanders of the Herbarium, Depart- our voucher specimens may someday find use. Also ment of Botany and Plant Sciences, University of Cali- reared in limited numbers from A. ilicifolia invo- fornia, Riverside, for identifying the plants mentioned in lucres infested by E. stiginatica were the following this study. The parasitoids were identified by G. Gordh chalcidoid Hymenoptera, that also presumably are when he was with the Systematic Entomology Labora- tory, USDA-ARS, Washington, DC. We also thank F. L. solitary, primary parasitoids: Heteroschema sp. Blanc, B. A. Foote, and P. Harris for their helpful com- (Pteromalidae) and ?Glyphomerus sp. (Torymi- ments on early drafts of the manuscript. dae). Biological Control. The role of E. aequalis as a seed predator of cocklebur, Xanthium strumar- References Cited ium L., has long been known (Marlatt 1891); ac- cordingly, it was one of the first insects exported Batra, S.W.T. 1979. 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